Vertebral artery hypoplasia and hemodynamic impairment in transient global amnesia: a case control study.

Introduction: The aetiology of transient global amnesia (TGA) is still a matter of debate. Besides ischemia of the mesial temporal lobe including the hippocampus, migraine-like mechanisms, epileptic seizures affecting mnestic structures, or venous congestion in the (para) hippocampal area due to jugular vein insufficiency have been discussed. We assessed the diameters of the intracranial arteries of TGA patients compared to controls to identify differences that support the hypothesis of reduced hippocampal perfusion as a pivotal factor in the pathophysiology of TGA. Methods: We reviewed magnetic resonance imaging time of flight angiographies (TOF-MRA) that were acquired during in-patient treatment of 206 patients with acute TGA. Results: The diameters of the vertebral artery (VA) in the V4 segment, the proximal basilar artery, and the internal carotid arteries were measured manually. We compared the findings with TOF-MRA images of an age and sex matched control group of neurological patients without known cerebrovascular pathology. In TGA patients the diameter of the right VA was significantly (p < 0.01) smaller compared to controls (2.09 mm vs. 2.35 mm). There were no significant differences in the diameters of the other vessels. Only the fetal variant of the posterior cerebral artery was slightly more common in TGA. Discussion: The smaller diameter (hypoplasia) of the right VA supports the hypothesis of a contribution of hemodynamic factors to the pathophysiology of TGA. The fact that hypoplasia represents a congenital condition might be the explanation why previous studies failed to find an increased rate of the classical (acquired) vascular risk factors.

Visual Evoked Potentials in Acute Retinal Migraine.

This case report describes monocular blurred vision and photopsia with headache.

Prevalence of Mimics and Severe Comorbidity in Patients with Clinically Suspected Transient Global Amnesia.

BACKGROUND: Transient global amnesia (TGA) is a syndrome featuring acute anterograde amnesia as the most striking clinical symptom. Its etiology is still a matter of debate. Most neurological guidelines allow the diagnosis on the basis of clinical criteria only; a more extensive evaluation is recommended only for patients with "red flags" like severe headache, nausea or vomiting, or metabolic abnormalities. The aim of our study was to assess the frequency of a severe underlying disease or alternative diagnoses (mimics) in patients fulfilling the clinical criteria. METHODS: We evaluated the medical records and the imaging data of an unselected consecutive cohort of patients with suspected TGA over a 7-year period. All patients were hospitalized and received a neurological workup including brain imaging, color-coded duplex sonography of the brain supplying arteries, electroencephalography, and laboratory studies of blood and (in selected cases) cerebrospinal fluid. RESULTS: 163 patients with 166 episodes of suspected TGA were hospitalized (3 patients twice). After the workup, the diagnosis of TGA was confirmed in 148/166 (89.2%) episodes ("simple TGA"). Eighteen patients (10.8%) either had an alternative diagnosis or a severe comorbidity that was assumed to have had an impact on the occurrence of the amnestic episode ("complicated TGA/mimic"). The most important differential diagnosis was stroke (11 patients, 6.6% of all TGA suspects and 61.1% of the complicated TGA/mimic group). Other mimics were transient epileptic amnesia (2 patients) and steroid-induced delirium (1 patient). Important comorbidities that had not been obvious at the time of presentation were severe sleep apnea (2 patients), triptan overuse (1 patient), and an involuntary amlodipine intoxication during TGA. CONCLUSION: As approximately every tenth patient with suspected TGA either had an alternative diagnosis or a severe comorbidity, which had not been obvious at the time of admission, we consider in-patient treatment of all suspected TGA cases as appropriate, preferably in the setting of a stroke unit, as ischemic stroke was the by far most important diagnosis mimicking TGA.

Increased incidence of transient global amnesia during the Covid-19 crisis?

Since the beginning oft he Covid-19 pandemic we have observed an increased incidence of transient global amnesia, possibly related to emotional stress as a trigger factor.

Facial angioedema and stroke.

BACKGROUND: Angioedema (AE) in stroke has been reported exclusively after thrombolysis with recombinant tissue-type plasminogen activator (rtPA). Previous studies proposed the insular cortex to play a specific role in the development of AE after stroke. We evaluated the incidence of AE in acute stroke and tried to identify the predominantly involved brain structures. METHODS: We performed a retrospective search of our stroke database for patients with an AE. MRI data were analyzed by adapting the images to a standard size and superimposing the infarctions. The areas of overlap were assumed to represent the areas of interest. RESULTS: 865 of 4,789 (18.1%) consecutive patients with acute stroke received IV rtPA, 20 of them (2.3%) developed AE. One patient developed AE without prior thrombolysis. The odds ratio for AE after rtPA was 93 (95% CI: 12-693). Of the 21 AE patients, 15 (71.4%) had ACE-inhibitor treatment (ACEi) and 7 (33.3%) had diabetes. In all but one patient, AE was clearly lateralized; then the AE was contralateral to the side of the ischemia in 18 of 20 patients (90.0%). An insular/peri-insular involvement was detected in 17/21 (81.0%). About 80.0% of the patients had a suspected MCA branch occlusion. CONCLUSIONS: In contrast to AE in other conditions, AE in stroke seems to feature a unique cerebral pathology because it is mostly lateralized (contralateral to an infarction), is associated with a distinct brain area, may even occur without rtPA, and is far more frequent than after thrombolysis for other indications. rtPA is the major risk factor. Similar to prior studies, we identified ACEi to be another risk factor, and a diabetic autonomic instability might further increase the risk. Central pathways involving the insular and peri-insular cortex seem to play a major role in the pathophysiology of AE in stroke.

Single-frequency Sb-based distributed-feedback lasers emitting at 2.3 microm above room temperature for application in tunable diode laser absorption spectroscopy.

GaInAsSb/GaAlAsSb/GaSb distributed-feedback (DFB) laser diodes based on a type I active region were fabricated by molecular beam epitaxy at the Centre d'Electronique et de Micro-Optoélectronique de Montpellier (CEM2). The DFB processing was done by Nanoplus Nanosystems and Technologies GmbH. The devices work in the continuous-wave regime above room temperature around an emission wavelength of 2.3 microm with a side-mode suppression ratio greater than 25 dB and as great as 10 mW of output power. The laser devices are fully characterized in terms of optical and electrical properties. Their tuning properties made them adaptable to tunable diode laser absorption spectroscopy because they exhibit more than 220 GHz of continuous tuning by temperature or current. The direct absorption of CH4 is demonstrated to be possible with high spectral selectivity.

Novel Helmholtz-based photoacoustic sensor for trace gas detection at ppm level using GaInAsSb/GaAlAsSb DFB lasers.

A new and compact photoacoustic sensor for trace gas detection in the 2-2.5 microm atmospheric window is reported. Both the development of antimonide-based DFB lasers with singlemode emission in this spectral range and a novel design of photoacoustic cell adapted to the characteristics of these lasers are discussed. The laser fabrication was made in two steps. The structure was firstly grown by molecular beam epitaxy then a metallic DFB grating was processed. The photoacoustic cell is based on a Helmholtz resonator that was designed in order to fully benefit from the highly divergent emission of the antimonide laser. An optimized modulation scheme based on wavelength modulation of the laser source combined with second harmonic detection has been implemented for efficient suppression of wall noise. Using a 2211 nm laser, sub-ppm detection limit has been demonstrated for ammonia.

Electron holography of thin amorphous carbon films: measurement of the mean inner potential and a thickness-independent phase shift.

The phase shift induced by thin amorphous carbon films with thicknesses between 1 and 16 nm was measured by electron holography in a transmission electron microscope. Large phase shifts Delta phi are observed as the thickness of the amorphous C films decreases which cannot be described by the well-known equation Delta phi = CE V0t (V0: mean inner Coulomb potential of the material, t: sample thickness). Data plotted in a Delta phi vs. t diagram can be well-fitted by a modified equation Delta phi=CE V0t + phi add. The mean inner Coulomb potential of the amorphous carbon with a density of 1.75 g/cm3 was determined to be 9.09 V which is consistent with previous experimental data for amorphous carbon with a higher density. The thickness-independent phase offset phi(add) of 0.497 rad is large for amorphous carbon under the given experimental conditions. We suggest that a surface-related electrostatic potential is responsible for the thickness-independent contribution phi add.

Application of antimonide diode lasers in photoacoustic spectroscopy.

First investigations of photoacoustic (PA) spectroscopy (PAS) of methane using an antimonide semiconductor laser are reported. The laser fabrication is made in two steps. The structure is firstly grown by molecular beam epitaxy, then a metallic distributed-feedback (DFB) grating is processed. The laser operates at 2371.6 nm in continuous wave and at room temperature. It demonstrates single-mode emission with typical tuning coefficients of 0.04 nm mA(-1) and 0.2 nm K(-1). PA detection of methane was performed by coupling this laser into a radial PA cell. A detection limit of 20 ppm has been achieved in a preliminary configuration that was not optimised for the laser characteristics.